1. Field of the Invention
The present invention relates to a short circuit inspection method executing a short circuit inspection during a prismatic battery manufacturing procedure to detect a short circuit caused by a shape of a current collector of a prismatic battery having an electrode plate group composed of a positive electrode plate, negative electrode plate and a separator, a prismatic battery manufacturing method including the short circuit inspection step, and a current collector shape adjusting device used in the prismatic battery manufacturing procedure to prevent a short circuit caused by a shape of the current collector.
2. Description of the Related Art
In recent years, portable information devices such as a cellular phone, note book-sized personal computer and so on have become widespread. Those devices aim for higher performance, reduced weight, and miniaturization. Accordingly, the secondary battery for use in the power supply of the portable information devices is required to have reduced size and weight and increased energy density. Further, such a secondary battery is used as a driving power source of an electric vehicle or a hybrid electric vehicle.
Such a portable information device, electric vehicle, or hybrid electric vehicle has limited space to house the secondary battery. On the other hand, the conventional secondary battery often has a cylindrical shape and thus undesirably creates a gap in the limited space so that a large space is required when it is housed.
Hence, in place of the cylindrical battery, a prismatic battery has become mainstream as a secondary battery used in the above devices or vehicles. Such a prismatic battery has an electrode plate group 10, in which side edge portions of positive electrode plates 18 and negative electrode plates 19 stacked via separators 17 on the opposite sides are protruded from facing areas of the both electrode plates, as shown in FIGS. 11A and 11B, and current collectors 20 are fixed to the protruded portions (lead portions 18a, 19a) in both side areas of the electrode plate group 10. Concretely, lead portion joint surfaces 24 of the current collector 20 face the lead portions 18a, 19a, bent portions 21, 21, bent from side ends of the respective lead portion joint surfaces 24 are formed to lie over outer surfaces of the electrode plate group 10 in a stack direction of the positive electrode plates 18 and negative electrode plates 19, and at least a part of the respective lead portion joint surface 24 is welded and fixed to the lead portions 18a, 19a. Further, an outer insulating tape 16 is attached on the outer surfaces of the positive electrode plate 18 and negative electrode plate 19 between the bent portions 21, 21 to insulate from the battery case 30.
When the current collectors 20 are fixed, the electrode plate group 10 is housed in the battery case 30, as a battery unit. The size of the battery case 30 is made close to the outside dimension of the electrode plate group 10 since it influences the outside dimension of the prismatic battery.
Regarding such a prismatic battery, the electrode plate group 10 is generally inspected whether or not a short circuit is generated in the electrode plate group 10 with the current collectors 20 before the electrode plate group 10 is housed in the battery case 30, as disclosed in Patent Document 1.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-236985
Patent Document 1 describes a technique of “A short circuit inspection method for a battery, in which an electrode plate group composed of positive electrode plates and negative electrode plates stacked via separators is inserted in a battery case, wherein a short circuit failure is inspected while applying pressure on the electrode plate group before inserting the electrode plate group into the battery case.” This technique is made in view of a short circuit failure caused by a swelling in the electrode plate group 10 by charges and discharges of the secondary battery, and the short circuit inspection is executed while applying pressure on a center portion of the electrode plate group 10 in a stack direction of the positive electrode plates and the negative electrode plates to virtually create a swelling condition.
Patent Document 2 proposes a technique for reducing a thickness of a circumference of a cut electrode plate to suppress an occurrence of burrs, which cause a short circuit.
[Patent Document 2] Japanese Patent Application Laid-Open No. 8-45500